1. Field of the Invention
The present invention relates to a method of coating the surface of inorganic powder particles with a silicon-carbon composite and to inorganic powder particles coated by the method. More particularly, the present invention relates to a method of coating the surface of inorganic powder particles with a silicon-carbon composite by mixing inorganic powder particles with a solid organic silicon polymer and heating the mixture, and to inorganic powder particles coated by the method.
2. Description of the Prior Art
A super-hydrophobic surface refers to a surface having a water contact angle of 150° or higher, and has self-cleaning, anti-fogging and water-proof functions. In nature, this phenomenon is observed in lotus or taro leaves and insect wings and legs and is referred to as the lotus effect. It is observed that the surface structures of the above leaves and insect wings and legs have a double structure of a micro-sized structure and a nano-sized structure. Namely, nano-sized protrusions are present on the surface of micro-sized structures to show the super-hydrophobic phenomenon in which water droplets roll down without adhering to the surface. This super-hydrophobic surface is applied in various fields, including inhibitors of the photocatalytic activity of cosmetic products, interior and exterior materials for buildings, organic and inorganic antioxidant films and waterproof fibers, and many studies thereon have been conducted.
In the prior art, many methods for obtaining super-hydrophobic surfaces were reported, including a method of increasing the water contact angle of a solid by controlling the surface roughness or a coating method which based on the self-assembly of hydrophobic organic molecules (e.g., stearic acid). Particularly, a method that uses organic molecules is widely used, because the organic molecules are strongly hydrophobic in nature. However, these organic molecules are significantly unstable so that they are easily degraded by light irradiation or the chemical composition thereof is changed.
Because UV rays cause various skin diseases, burns, cancer and the like, the harmfulness of UV rays has been increasingly recognized and agents for blocking UV rays have been developed. UV blocking agents can be broadly divided into inorganic UV scattering agents and organic UV absorbents. The organic UV absorbents absorb mainly middle-wavelength UV light and convert the light to vibration or fluorescence energy, thus protecting the skin from the light. On the other hand, the inorganic UV scattering agents scatter and block long-wavelength UV light, and specific examples thereof include titanium dioxide, zinc oxide, zirconium oxide and the like. The inorganic UV blocking agents are more stable than the organic UV blocking agents and can block off a wide range of UV light, and thus have received increasing attention. Particularly, titanium dioxide has a high refractive index, and thus can effectively scatter and block light. In addition, it is harmless to the human body. Due to such advantages, titanium dioxide is frequently used as a UV blocking agent. However, titanium dioxide shows high photoactivity when it is irradiated with UV light. Thus, when it is used together with other cosmetic materials, it degrades or modifies these cosmetic materials. In addition, it can produce strongly oxidative OH radicals or O2−, which can promote skin aging. For this reason, efforts have been made to coat the surface of these UV blocking agents with a thin film, thus scattering or absorbing UV while inhibiting the photoactivity of the UV blocking agents.
With the accelerated development of display devices and electronic energy devices, the development of printing technology has become essential in various fields, including electronic device processes, material manufacturing processes, and biotechnology, and studies thereon have been actively conducted. In addition, the printing method is inexpensive, is not complicated and is not time-consuming, and thus is frequently used in industrial applications. For example, in the display field, an inkjet printing technique is used in a process of obtaining patterns using conductive metal nanopowder. However, the printing process has a problem in that the metal powder is oxidized when it is heat-treated or dispersed in a solvent, and thus the conductivity thereof is reduced. In order to solve this problem, the development of a coating technique for forming a film for preventing the oxidation of metal powder is urgently required.
Accordingly, the present inventors have conducted studies in view of the above problems, and as a result, have found that, when the surface of inorganic powder particles is coated with a solid organic silicon polymer using a vapor deposition method by mixing the inorganic powder particles with the solid organic silicon polymer and heating the mixture, a coating film can be formed which is thin and uniform compared to that formed by a liquid coating method, and also found that the coating film is highly stable against UV light and has an antioxidant effect, thereby completing the present invention.